Graffiti battery lets you spray paint power supply

Run out of batteries? Just spray-paint some new ones. Researchers have created five sprayable paints that form a lithium-ion battery when layered together, letting you store energy on walls, tiles or even your favourite mug.

Regular batteries contain a positive and negative electrode, both paired with a metal current collector, and a polymer separator sandwiched in the middle. These five layers are normally manufactured in sheets and rolled up into a cylinder, making it hard to create extremely thin batteries.

Now, Neelam Singh and colleagues at Rice University in Houston have used a combination of existing metallic paints and custom materials to create sprayable versions of each layer, allowing them to make batteries just a fraction of a millimetre thick by airbrushing the layers onto a surface, one at a time.

The team applied their batteries to a variety of ordinary building materials and even a ceramic drinks mug to test their potential. Nine bathroom tile batteries charged by a solar cell were able to power 40 LEDs arranged to spell out "RICE" for six hours. They don't yet match regular batteries – a paintable battery would have to be about 1.5 square feet to match a standard mobile phone battery – but that is set to improve. "Their capacity, efficiency and performance could be vastly improved if made on an industrial scale," explains Singh.

Pairing the batteries with recently developed paintable solar cells could potentially give your walls an electrifying DIY makeover, but Singh says the paints are not quite ready for home use, as paints must be applied in a moisture- and oxygen-free environment onto surfaces heated to 120 °C.

"The focus of our ongoing research is to develop new battery materials which would not be degraded by air or moisture, non-toxic and safe to handle and use at home by non-experts, and environmentally friendly during use and disposal," says Singh. Only then will you be able to pick up a few spray cans and build your own batteries.

"I don't think people will be doing this at home, but maybe secondary manufacturers would be painting on batteries," says John Owen, a chemist who researches batteries at the University of Southampton, UK. For example, there are already companies that will gold-plate your iPhone – perhaps they could also add an extra battery coating.

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The lithium-ion batteries can be painted on virtually any surface (Image: Jeff Fitlow/Rice University)